Liquid crystalline polymers (LCPs) are items of commerce, thousands of tons being made annually. They are used in a myriad of ways, as molding resins and in films, for example to make electrical and electronic parts, automotive parts, and medical parts. LCPs are most often provided as polyesters, but also available as poly(ester-amides). The condensation reaction to form the polyester linkages is most commonly done by condensing at elevated temperatures one or more dicarboxylic acids with the aliphatic esters of one or more diols and/or the aliphatic monoesters of one or more hydroxycarboxylic acids. Although the aliphatic esters can be “preformed”, that is, the ingredients added to the polymerization process as aliphatic esters, for economic reasons the aliphatic esters are usually made in situ by adding an appropriate amount of an aliphatic carboxylic anhydride to the polymerization mixture to form the aliphatic ester(s).
Typically all of the monomers needed to form the LCP are added to a reactor together with an amount of aliphatic carboxylic anhydride, usually acetic anhydride, to form ester groups with all of the hydroxyl groups of the diols and hydroxycarboxylic acids monomer present in the ester groups. The mixture is heated to complete ester formation and the carboxylic acid formed is removed by distillation. Heating is continued, with concomitant distillation of carboxylic acid, to perform the condensation polymerization, and finally usually vacuum is applied to complete the polymerization. Alternately melt polymerization can be discontinued at some point and the (pre)polymer further polymerized to the desired molecular weight using so-called solid state polymerization. It may be desirable, particularly when one of the diols used is somewhat volatile, to use an excess of the diol in the polymerization, to make up for any possible losses of the diol (or its diester) by inadvertent volatilization and removal from the polymerization. However, the LCPs obtained may not have optimal properties for desired uses, and in particular can be more brittle than desired for some applications.
U.S. Pat. No. 6,294,618 describes the treatment of LCPs with various functional compounds to reduce the viscosity of the LCPs.
LCPs having improved properties, such as tensile or flexural elongation, are desirable.